Editing Membrane keyboard (section)

== Mechanism ==
[[file:Membrane keyboard diagram FULL SCALE.png|thumb|Cross-section diagram of a typical membrane keyboard. The thickness of the bottom three layers has been exaggerated for clarity; in reality, they are not much thicker than pieces of paper or thin cardstock.]]

The membrane (typically made out of [[Polyethylene terephthalate]] or PET) keyboard consists of three layers: two layers containing traces of [[conductive ink]] and the center layer is a "spacer" containing holes wherever a two conductive "key" pads count touch upon being pressed. The third layer keeps the other two layers separated in order to prevent [[short-circuit]].<ref>{{Cite book |last=Thompson |first=Robert Bruce |url=https://books.google.com/books?id=kG8LcWfruOAC |title=PC Hardware in a Nutshell: A Desktop Quick Reference |last2=Thompson |first2=Barbara Fritchman |date=2003-07-24 |publisher=[[O'Reilly Media, Inc.]] |isbn=978-0-596-55234-3 |pages=603 |language=en}}</ref><ref name=":0" />

Under normal conditions, the switch (key) is open, because current cannot cross the non-conductive gap between the traces on the bottom layer. However, when the top layer is pressed down (with a finger), it makes contact with the bottom layer. The conductive traces on the underside of the top layer can then bridge the gap, allowing current to flow. The switch is now "closed", and the parent device registers a keypress.{{Citation needed|date=August 2024}}

Many applications benefit from the sealed nature of the membrane keypad. Feedback can easily be provided to the user via audible means (e.g. a beep) or visually (lights or via the display itself), or via both means together. For additional wear resistance, a simple, easily replaceable protective clear sheet can be placed in front of the membrane. Membrane keyboards are widely used in consumer electronics, industrial, commercial, scientific and military equipment.{{Citation needed|date=August 2024}}

[[File:Inside Computer keyboard.jpg|thumb|Internal layers of a modern full-travel computer keyboard; bottom contact layer, spacer layer with holes, top contact layer, then elastomer top layer to provide restoring force to keytops.]]